1. Field of the Invention
The present invention relates to a liquid ejection head, a manufacturing method thereof, and an image forming apparatus, and more particularly to a technique for connecting electric wires provided at a high density in a liquid ejection head.
2. Description of the Related Art
An inkjet printer (inkjet recording apparatus) having an inkjet head (liquid ejection head) in which a large number of nozzles (ejection ports) are arranged is known as an image forming apparatus. This inkjet printer records an image on a recording medium by depositing ink on the recording medium from the nozzles while moving the inkjet head relative to the recording medium.
In this type of inkjet printer, ink is supplied from an ink tank to a pressure chamber through an ink supply passage. A piezoelectric element is then driven by applying to the piezoelectric element an electric signal corresponding to image data, whereby a diaphragm constituting a part of the pressure chamber is deformed such that the volume of the pressure chamber decreases. As a result, the ink in the pressure chamber is ejected from the nozzle in liquid droplet form.
In this type of inkjet printer, a single image is formed on the recording medium by combining dots formed by the ink ejected through the nozzles. In recent years, demands have been made of inkjet printers for high-quality image formation on a par with photographic prints. To realize such high image quality, it is possible to reduce the size of the ink droplets ejected through the nozzles by decreasing the nozzle diameter, and also to increase the number of pixels per unit area by arranging the nozzles at a higher density.
To increase the density of the nozzle array, the structure of electric wires for driving the nozzles and a method of connecting the electric wires to electrodes must be devised. Various proposals relating to these problems have been made.
For example, an apparatus is known in which a nozzle is disposed on a piezoelectric element side, a structure in which an aluminum plug passes through laminated layers is employed, and the head is formed by silicon photoetching. In so doing, an attempt is made to increase density and reduce costs (see Japanese Patent Application Publication No. 2000-289201, for example).
As another example, an apparatus is known in which a porous member made of sintered stainless steel or the like and having a large number of internally-connected small holes is used as an ink supply plate so that ink can pass through this part. In so doing, an attempt is made to realize an inkjet head having excellent refill, ink mixing, and filtration properties (see Japanese Patent Application Publication No. 2003-512211, for example).
In another example, an attempt is made to simplify the structure by connecting a drive wire to a packaging portion provided in an area on the opposite side to a piezoelectric element (see Japanese Patent Application Publication No. 2003-136721, for example).
However, in the apparatus described in Japanese Patent Application Publication No. 2000-289201, for example, a structure in which an aluminum plug passes through laminated layers is employed, but since the head is formed by silicon photoetching, it is difficult to form deep electrodes and increase the size of the head.
In the apparatus described in Japanese Patent Application Publication No. 2003-512211, bumps are formed on both sides of an insulation plate, and electrodes are extracted by applying pressure to the piezoelectric element using an elastic pad. With this constitution, however, it is difficult to achieve an increase in density, and the connections are likely to become unstable.
In the apparatus described in Japanese Patent Application Publication No. 2003-136721, it is difficult to form narrow, deep wires due to the disclosed wiring pattern, wire bonding connection, and method of extracting electrodes using thin plates.